One known piezoelectric printer prints one dot by an impact established by applying a printing pulse voltage to a piezoelectric element fixed to a lever spring. The pulse drives the spring to thereby move a printing wire attached to the lever spring. Thus, such a piezoelectric printer can be more compact than the printer of electromagnetic drive type.
Since the printing energy has to be generated by the single action of the piezoelectric element, this element has to be enlarged or driven with a high voltage. Thus, the problem arises that the heat structure is complicated and that the electric power requirements are increased.
Moreover, gradation of the printing is effected by a netting method and is accompanied by the problem that a complicated driver is required. If 16 gradations are required, for example, one dot is imagined to be composed of 4.times.4 pixels so that a gradation of multiple stages for the printing density may be achieved by printing all the 16 pixels for a deep black but none of the pure white, and by printing a proper number of pixels for a half tone. In order to effect gradation in this netting method, it is necessary to provide a complicated driver for controlling which pixel is to be printed according to the stage of half tone.